Dynamic readjustment of parental methylation patterns of the 5 '-flank of the mouse H19 gene during in vitro organogenesis

Gametic marks are stably propagated in order to manifest parent of origin-s pecific expression patterns of imprinted genes in the developing conceptus. Although the character of the imprint has not yet been fully elucidated, t here is compelling evidence that it involves a methylation mark. This is ex emplified by a region upstream of the H19 gene, which is not only methylate d in a parent of origin-specific manner, but also regulates the silencing o f the maternal Igf2 and paternal H19 alleles, respectively. We show here th at the parental-specific methylation patterns within the differentially met hylated domain (DMD) are perturbed in the soma during in vitro organogenesi s. Under these conditions, the paternal DMD allele becomes partially demeth ylated, whereas the maternal DMD allele gains methylation. Despite these ef fects, there were no changes in allelic Igf2 or H19 expression patterns in the embryo. Finally, we show that although TSA derepresses the paternal H19 allele in ectoplacental cone when in vitro developed, there is no discerni ble effect on the methylation status of the paternally inherited 5'-flank i n comparison to control samples. Collectively,this data demonstrates that t he parental mark is sensitive to a subset of environmental cues and that a certain degree of plasticity of the gametic mark is tolerated without affec ting the manifestation of the imprinted state.